Twisted tuft or knot type wire brushes, whether of the wheel or cup type, have long been employed. Examples may be seen in Peterson U.S. Pat. Nos. 2,929,086, 2,866,989, and 2,826,776. In this well known type of brush, bundles of wire are inserted through equally circumferentially spaced holes in an annulus or within a retaining ring. The tufts are folded to extend radially and then twisted on themselves to form a twisted knot type brush. The tufts, whether one or a few turns, or many, are twisted as tight as possible, both to secure the wire in place to the annulus or ring, but also to cause the wires mutually to reinforce each other, both within the twisted tuft or knot, and adjacent knots. One of the principal advantages of this type of tool is that the working tips of the wires or filaments each point in a slightly different direction, providing an aggressive cutting, deburring or abrading action.
Such tools have a few disadvantages. One is that they require a lot of what can be expensive wire. They are costly to make correctly, and they suffer from wire fatigue and fracture. Moreover, it is difficult to control and maintain uniform wire point distribution. Where a narrow brush face is desired, the tufts are twisted tight to their working tips providing radially separating tight narrow bundles. To provide a wider more dense face, several rows with fewer twists may be provided. The distribution at the working face is still a problem. While the wire tip may be pointing in the right direction to do the job, if it is too easily laterally deflected or insufficiently supported, it may miss its opportunity. Accordingly, it would be desirable to provide a lower cost twisted tuft or knot type wire brush and yet with a more uniform and better supported wire tip working face.
Foamed elastomers have long been used to improve the working action of rotary brushes. Examples are the wide line of TY.RTM. brushes sold by Osborn Manufacturing of Cleveland, Ohio. A more recent example is seen in Schneider et al. U.S. Pat. Nos. 4,945,687 and 5,046,288.
Attempts to provide the advantages of a foamed elastomer matrix to a twisted tuft or knot type brush have failed, perhaps for a variety of reasons. The principal reason is the tuft or knot form of the tool. The tuft form and material viscosities do not allow the elastomer to penetrate the tight twist or knot. The elastomer is instead concentrated at the sides between the tufts or knots and often times in isolated pockets which may tend to break out or become dislodged during use. Abrasives or fillers in the elastomers designed to erode the elastomer in use do not get where they can do some good and just make the unwanted disintegration problem worse. An elastomer useful in a twisted tuft or knot tool needs to have a high tensile strength, low viscosity and an appropriate hardness level. The elastomer also needs good thermal stability.
It would, accordingly, be desirable to have a twisted tuft or knot type brush where the advantages of a foamed elastomer matrix could be employed to provide more uniform wire point distribution with good requisite lateral support and control, all at a lower cost.